Topics covered in this Lesson:

For the next few lessons, you should switch to the 3D modeling workspace. Look for the icon in the bottom right of the AutoCAD screen.

What is a Primitive Solid?

A primitive solid is a ‘building block' that you can use to work with in 3D. Rather than extruding or revolving an object, AutoCAD has some basic 3D shape commands at your disposal. From these basic primitives, you can start building your 3D models. In many cases, you get the same result from drawing circles and rectangles and then extruding them, but doing it one command is generally faster. Using these with Boolean operations can be a very effective way of drawing in 3D. There are eight different primitives that you can choose from and are on the Home > Modeling Tool Panel (when in the 3D workspace).

(Click on the ICON below to go to the command)

SHAPE

COMMAND

ICON

DESCRIPTION

BOX

BOX

Creates a solid box after you provide 2 opposite corners and a height.

SPHERE

SPHERE / SPH

Creates a solid sphere from a center point and radius.

CYLINDER

CYLINDER / CYL

Creates a straight cylinder from a center point, radius and height.

CONE

CONE

Creates a tapered cone from a center point, radius and height.

WEDGE

WEDGE / WED

Creates a triangular wedge from 2 opposite points.

TORUS

TORUS / TOR

Creates a torus (donut shape) based on center point, radius and tube radius.

PYRAMID

PYRAMID / PYR

Draws a solid object with a polygon (3-32 sides) base that rises to a central point.

POLYSOLID

PSOLID

Draws a solid object with width and height as you would draw a polyline.

You can use primitives to either begin building a model or it can be a finished object on its own. Many of these commands are similar to 2D commands, except with an extra coordinate in the Z axis. Here is a summary of working with these commands.

BOX

Think of a box as an extruded rectangle. It has width, height and depth. It is created by establishing a starting corner and then establishing a second corner by either picking or giving relative coordinates.

Of course you can also draw a box by picking two opposite corners with your mouse. This is useful for filling in areas and can be very quick. Make sure to use your Osnaps.

SPHERE

A Sphere is a globe-like shape. It is very similar to drawing a circle in that you pick a center point and then input either the radius (default) or diameter. Both methods draw the same sphere in the following examples:

Another way of drawing a cone is to enter in the center point, the radius (or diameter) and then establish where you want the apex (point of cone) to be. You can either type in coordinate points or pick a point with your cursor.

WEDGE

One of the trickier primitives to draw is the wedge. You have to be careful which coordinates you input to make the wedge lie in the position you want. If it doesn't turn out just as you hoped for, you can always rotate it.

Once the first corner is established, you can either enter points, or pick a spot. AutoCAD will draw the shape like it would draw a cube except it is slice in half along the length starting at the point above the first corner. There are other options to drawing wedges and see the box examples for these.

TORUS

A torus is a donut-like shape or something resembling an inner tube. When drawing one you have to enter the center point, a radius to the center of the tube and the radius of the tube itself.

The diagram above shows the resulting diameters from the input above. A center mark indicates the picked center of the torus.

PYRAMID

To draw a pyramid, you need to know the diameter of the base and the height. The diameter can either be inscribed (inside the circle) or circumscribed (outside the circle). You can define the number of edges to from 3 to 32.

Specify base radius or [Inscribed] <4.5655>: I

Specify base radius or [Circumscribed] <4.5655>: 4

Specify height or [2Point/Axis endpoint/Top radius] <10.0108>: 9

In the above example, I showed how to switch between Inscribed or Circumscribed as the options change depending upon the method selected.

Try creating some pyramids using a variety of methods.

POLYSOLID

This is a new command since AutoCAD 2007. A polysolid allows you to draw a solid object while defining the height and the width. I think this command is aimed at the architects, who will enjoy the ability to quickly draw solid walls.

REVIEW

As mentioned in previous lessons, solids are usually the way to go with 3D CAD. Depending upon your chosen field, you may use 3D meshes in Civil Drafting, Isometric in HVAC, solids in mechanical, etc.

I recommend getting used to solids if you are doing any kind of mechanical drafting or architectural drafting if you are using base AutoCAD software. When using solids, you will usually take a shape and extrude it - then use boolean commands and others to edit it. Here is a basic building that was quickly drawn using a variety of primitive solids.

Extra Practice: Draw some primitive solids using the dimensions shown above or make up your own. Try to create a building out primitive solids.

Video: Creating Primitive Solids

Take the Lesson 3-10 Quiz

For Further Thought:

Here's a set of tools that come in a separate case that fits perfectly in your 3D toolbox. When do you choose to use them? When you draw a box instead of extruding a rectangle? When do you use a wedge? I can't tell you that. You need to learn the tools, remember how to use them and then pull them out at the right time. Many designers will use these tools at the early design stage to visualize space and work with concepts of how these shape might work in the environment. Think of how your could quickly assemble some 3D blocks to visualize the shape of an apartment block and then place it in a photo. This tutorials isn't about how to draw a cube, it's about how to visualize.

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